Comment on: Individualized Corneal Cross-linking With Riboflavin and UV-A in Ultrathin Corneas: The Sub400 Protocol

•The standard cross-linking protocol is limited to corneas with a stromal thickness of more than 400 μm.•We introduce a new treatment modality that, predicting penetration depth, allows the cross-linking of ultrathin corneas using individualized fluence.•The “sub400” individualized fluence corneal cross-linking protocol halted keratoconus progression with a success rate of 90% at 12 months.